Model
Model explorer

GPT-5.6 Luna

CLOSED
OpenAI · GPT-5.6 family · released Jul 9, 2026

Cheapest/fastest tier of the three-tier GPT-5.6 family (GA July 9, 2026 alongside Sol and Terra); OpenAI positions the tiers as 'durable capability tiers that can advance on their own cadence' — Luna targets cost-sensitive, high-volume workloads. Same 1.05M context, 128K max output and Feb 2026 knowledge cutoff as Sol, at a fifth of Sol's price ($1/$6 vs $5/$30 per MTok). Distinct model tier, not a reasoning-effort configuration of Sol (each tier separately exposes its own effort settings).

ReasoningCodingVisionFunction callingTool useAgentic
2651.5
Elo · rank #22
Parameters
Undisclosed
Active params
—
Context
1.05M tokens
Architecture
Undisclosed architecture (presumed dense transformer); fastest/cheapest 'durable capability tier' of the GPT-5.6 Sol/Terra/Luna family, built for cost-sensitive high-volume workloads
License
Proprietary
Languages
—
API price (in/out)
$1 / $6
Modalities
text · vision
Benchmark results
Bar shows position within the tracked field; marker = field best
Agents' Last ExamAgents50.3%#5
best: GPT-6 Astra · 59.3%
BrowseCompAgents83.3%#15
best: Kimi K3 · 91.2%
CyberGymCoding77.9%#6
best: GLM-5.3 · 84.5%
FrontierBenchAgents14.3%#8
best: Claude Opus 5 · 43.3%
FrontierMath (Tiers 1-3)Math78.6%#3
best: GPT-5.6 Sol · 89.0%
FrontierMath (Tier 4)Math58.5%#3
best: GPT-5.6 Sol · 83.0%
GDPval-AAAgents1591.8#15
best: Claude Fable 5 · 1932
GPQA DiamondReasoning92.3%#19
best: GPT-6 Astra · 96.0%
MMMU-ProVision78.4%#19
best: Claude Opus 4.7 · 85.5%
SWE-bench ProCoding62.7%#11
best: Claude Fable 5.1 · 81.2%
τ³-BankingAgents27.2%#4
best: GPT-5.6 Sol · 33.0%
Terminal-Bench 2.0Coding84.7%#9
best: Gemini 3.8 Flash · 89.4%
Run it locally
Closed weights — available via API only. No local deployment.
Input / M tok
$1
Output / M tok
$6
GPT-5.6 family
Elo progression across releases
GPT-5.6 LunaJul 20262651.5GPT-5.6 SolJul 20262915.3GPT-5.6 TerraJul 20262688.0GPT-5.6 CyberAug 20261000.0
Resources
DOCSdevelopers.openai.com/api/docs/models/gpt-5.6-lunaAPIAvailable via OpenAI API
API price $1/$6 · each benchmark row carries its own source badge (see methodology)